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<pre><span class="sourceLineNo">001</span>/*<a name="line.1"></a>
<span class="sourceLineNo">002</span> * Copyright (C) 2007 The Guava Authors<a name="line.2"></a>
<span class="sourceLineNo">003</span> *<a name="line.3"></a>
<span class="sourceLineNo">004</span> * Licensed under the Apache License, Version 2.0 (the "License");<a name="line.4"></a>
<span class="sourceLineNo">005</span> * you may not use this file except in compliance with the License.<a name="line.5"></a>
<span class="sourceLineNo">006</span> * You may obtain a copy of the License at<a name="line.6"></a>
<span class="sourceLineNo">007</span> *<a name="line.7"></a>
<span class="sourceLineNo">008</span> * http://www.apache.org/licenses/LICENSE-2.0<a name="line.8"></a>
<span class="sourceLineNo">009</span> *<a name="line.9"></a>
<span class="sourceLineNo">010</span> * Unless required by applicable law or agreed to in writing, software<a name="line.10"></a>
<span class="sourceLineNo">011</span> * distributed under the License is distributed on an "AS IS" BASIS,<a name="line.11"></a>
<span class="sourceLineNo">012</span> * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.<a name="line.12"></a>
<span class="sourceLineNo">013</span> * See the License for the specific language governing permissions and<a name="line.13"></a>
<span class="sourceLineNo">014</span> * limitations under the License.<a name="line.14"></a>
<span class="sourceLineNo">015</span> */<a name="line.15"></a>
<span class="sourceLineNo">016</span><a name="line.16"></a>
<span class="sourceLineNo">017</span>package com.google.common.collect;<a name="line.17"></a>
<span class="sourceLineNo">018</span><a name="line.18"></a>
<span class="sourceLineNo">019</span>import com.google.common.annotations.Beta;<a name="line.19"></a>
<span class="sourceLineNo">020</span>import com.google.common.annotations.GwtCompatible;<a name="line.20"></a>
<span class="sourceLineNo">021</span><a name="line.21"></a>
<span class="sourceLineNo">022</span>/**<a name="line.22"></a>
<span class="sourceLineNo">023</span> * A constraint that an element must satisfy in order to be added to a<a name="line.23"></a>
<span class="sourceLineNo">024</span> * collection. For example, {@link Constraints#notNull()}, which prevents a<a name="line.24"></a>
<span class="sourceLineNo">025</span> * collection from including any null elements, could be implemented like this:<a name="line.25"></a>
<span class="sourceLineNo">026</span> * &lt;pre&gt;   {@code<a name="line.26"></a>
<span class="sourceLineNo">027</span> *<a name="line.27"></a>
<span class="sourceLineNo">028</span> *   public Object checkElement(Object element) {<a name="line.28"></a>
<span class="sourceLineNo">029</span> *     if (element == null) {<a name="line.29"></a>
<span class="sourceLineNo">030</span> *       throw new NullPointerException();<a name="line.30"></a>
<span class="sourceLineNo">031</span> *     }<a name="line.31"></a>
<span class="sourceLineNo">032</span> *     return element;<a name="line.32"></a>
<span class="sourceLineNo">033</span> *   }}&lt;/pre&gt;<a name="line.33"></a>
<span class="sourceLineNo">034</span> *<a name="line.34"></a>
<span class="sourceLineNo">035</span> * In order to be effective, constraints should be deterministic; that is,<a name="line.35"></a>
<span class="sourceLineNo">036</span> * they should not depend on state that can change (such as external state,<a name="line.36"></a>
<span class="sourceLineNo">037</span> * random variables, and time) and should only depend on the value of the<a name="line.37"></a>
<span class="sourceLineNo">038</span> * passed-in element. A non-deterministic constraint cannot reliably enforce<a name="line.38"></a>
<span class="sourceLineNo">039</span> * that all the collection's elements meet the constraint, since the constraint<a name="line.39"></a>
<span class="sourceLineNo">040</span> * is only enforced when elements are added.<a name="line.40"></a>
<span class="sourceLineNo">041</span> *<a name="line.41"></a>
<span class="sourceLineNo">042</span> * @see Constraints<a name="line.42"></a>
<span class="sourceLineNo">043</span> * @see MapConstraint<a name="line.43"></a>
<span class="sourceLineNo">044</span> * @author Mike Bostock<a name="line.44"></a>
<span class="sourceLineNo">045</span> * @since 3.0<a name="line.45"></a>
<span class="sourceLineNo">046</span> */<a name="line.46"></a>
<span class="sourceLineNo">047</span>@Beta<a name="line.47"></a>
<span class="sourceLineNo">048</span>@GwtCompatible<a name="line.48"></a>
<span class="sourceLineNo">049</span>public interface Constraint&lt;E&gt; {<a name="line.49"></a>
<span class="sourceLineNo">050</span>  /**<a name="line.50"></a>
<span class="sourceLineNo">051</span>   * Throws a suitable {@code RuntimeException} if the specified element is<a name="line.51"></a>
<span class="sourceLineNo">052</span>   * illegal. Typically this is either a {@link NullPointerException}, an<a name="line.52"></a>
<span class="sourceLineNo">053</span>   * {@link IllegalArgumentException}, or a {@link ClassCastException}, though<a name="line.53"></a>
<span class="sourceLineNo">054</span>   * an application-specific exception class may be used if appropriate.<a name="line.54"></a>
<span class="sourceLineNo">055</span>   *<a name="line.55"></a>
<span class="sourceLineNo">056</span>   * @param element the element to check<a name="line.56"></a>
<span class="sourceLineNo">057</span>   * @return the provided element<a name="line.57"></a>
<span class="sourceLineNo">058</span>   */<a name="line.58"></a>
<span class="sourceLineNo">059</span>  E checkElement(E element);<a name="line.59"></a>
<span class="sourceLineNo">060</span><a name="line.60"></a>
<span class="sourceLineNo">061</span>  /**<a name="line.61"></a>
<span class="sourceLineNo">062</span>   * Returns a brief human readable description of this constraint, such as<a name="line.62"></a>
<span class="sourceLineNo">063</span>   * "Not null" or "Positive number".<a name="line.63"></a>
<span class="sourceLineNo">064</span>   */<a name="line.64"></a>
<span class="sourceLineNo">065</span>  @Override<a name="line.65"></a>
<span class="sourceLineNo">066</span>  String toString();<a name="line.66"></a>
<span class="sourceLineNo">067</span>}<a name="line.67"></a>




























































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